Material for magnetic transducer heads

Abstract

A magnetic head assembly wherein the material of the pole tips or of the pole pieces comprises a hot-pressed sintered iron-silicon-aluminum alloy, the particles of such alloy preferably being provided with a nitride layer or coating prior to sintering for preventing or retarding grain growth during sintering and to provide increased electrical resistivity and hardness in the end product. The preferred hot-pressed sintered material is characterized by a substantially uniform grain size most preferably of between about 40 microns and 60 microns, a porosity of substantially less than one percent, a Vickers hardness greater than 600, and a resistivity of at least about 100 micro-Ohm-cm. A method of making such a sintered material preferably comprises heating an iron-silicon-aluminum alloy powder in an atmosphere of nitrogen to form a nitride layer thereon, blending 80% of such nitrided alloy powder with from about 10 to 20% of elemental iron, silicon and aluminum powders, without varying the composition from that desired in the final alloy, and heating the mixture to a sintering temperature while applying a pressure of about 1000 pounds per square inch.

I claim as my invention: 
     
       1. A hot-pressed sintered magnetic material consisting essentially of an alloy having an aluminum content of 4 to 6.5% by weight and a silicon content from 8 to 11% by weight, with the remainder substantially iron, said sintered magnetic material being characterized by a porosity of substantially less than 1%, a Vickers hardness greater than 600 (measured at a 300 gram load) and a resistivity of at least 100 micro-Ohm-centimeters. 
     
     
       2. A magnetic head assembly comprising: a pole piece construction having a gap for coupling to a magnetic record medium,   said pole piece construction being comprised of hot-pressed sintered magnetic material formed predominantly from nitrided particles of an aluminum-silicon-iron alloy, having a substantially increased resistivity (as compared with non-nitrided material) of at least about 100 micro-Ohm-centimeters,   said pole piece construction having a porosity of substantially less than one percent and a Vickers hardness substantially greater than 600 (measured at a 300 gram load).   
     
     
       3. A magnetic head assembly as defined by claim 2, wherein said nitrided particles of the sintered magnetic material have a substantially uniform size varying not more than 50% from a mean grain size and lying within the range from about 10 microns to about 500 microns.   
     
     
       4. A magnetic pole piece formed of hot-pressed sintered magnetic material having an aluminum content of 4 to 9% by weight, and a silicon content of 6 to 12% by weight, with the remainder essentially iron, said hot-pressed sintered magnetic material having a porosity of less than about 0.1%, a Vickers hardness greater than 600 (measured at a 300 gram load), a grain size of a substantially uniform dimension within a size range of between about 40 microns and about 60 microns, a resistivity of at least 100 micro-Ohm-centimeters, and an initial permeability of about 15,000. 
     
     
       5. A magnetic transducer head assembly comprising: a pole piece construction having a gap for coupling to a magnetic tape record medium,   said pole piece construction comprising a sintered magnetic material for sliding contact with the tape record medium and comprising predominantly a magnetic nitrided iron-silicon-aluminum alloy,   the sintered magnetic material having a substantially uniform grain size varying not more than 50% from a mean grain size and lying within the range from about 10 microns to about 500 microns.   
     
     
       6. A hot-pressed sintered magnetic material comprising predominantly nitrided sintered grains of an aluminum-silicon-iron alloy, said mataerial having a resistivity of at least 100 micro-Ohm-centimeters, a porosity of less than 1 percent and a Vickers hardness substantially greater than 600 (measured at a 300 gram load).